Twice reflected ultrasonic bulk wave for surface defect monitoring.

This work offers an ultrasonic structural health monitoring (SHM) approach for assessing the defects located on the same surface and at one side of piezoelectric ultrasonic transducer array. It is based on the analysis of ultrasonic bulk wave travelling in the thickness direction obtained from an enhanced full-skip configuration of the time-of-flight diffraction (TOFD) technique. In contrast to existing TOFD setup only considering the direct paths between the ultrasonic transducer and defect, our ultrasound monitoring configuration involves twice reflected ultrasonic bulk wave (TRBW).

Mechanism of airborne sound absorption through triboelectric effect for noise mitigation.

Mitigating broadband noise with passive airborne sound absorbers has been a long-lasting challenge, particularly for low-frequency anthropogenic sounds below kilohertz with long wavelengths, which require bulky materials for effective absorption. Here, we propose a strategy that utilizes local triboelectric effect and in-situ electrical energy dissipation mechanism for airborne sound absorption. This approach involves a fundamentally different mechanism that converts airborne sound into electricity for energy dissipation, in contrast to conventional mechano-thermal energy conversion mechanisms.

Inhibitory effect of silver nanoparticles synthesized using the chamomile extract against Streptococcus mutans cariogenic pathogen.

Background: With the recent use and development of nanomaterials, silver nanoparticles (AgNPs) are gaining much attention as a promising antibacterial agent for use in caries prevention.

Objectives: This study aimed to biosynthesize AgNPs using chamomile extract as a reducing agent and to investigate its inhibitory effect against Streptococcus mutans (S. mutans) dental bacteria.

Effectiveness of buccal infiltration anaesthesia compared to inferior alveolar nerve block anaesthesia in primary mandibular molar extractions: a randomised controlled study.

Aim The current study assessed the efficiency of buccal infiltration (BI) and inferior alveolar nerve block (IANB) during the extraction of deciduous mandibular molars.Subjects and method A total of 112 children aged between 5-8 years with mandibular molar indicated for extraction were divided into two groups at random. The BI group was injected with 4% articaine using BI, while the IANB group was injected with 2% lidocaine using IANB.

Surface Crack Monitoring by Rayleigh Waves with a Piezoelectric-Polymer-Film Ultrasonic Transducer Array.

This paper presents a method for measuring surface cracks based on the analysis of Rayleigh waves in the frequency domain. The Rayleigh waves were detected by a Rayleigh wave receiver array made of a piezoelectric polyvinylidene fluoride (PVDF) film and enhanced by a delay-and-sum algorithm. This method employs the determined reflection factors of Rayleigh waves scattered at a surface fatigue crack to calculate the crack depth.

Sound Absorption Improvement in Porous Ferroelectret Polyethylene with Effective Piezoelectric Mechanism.

Airborne sound absorption in porous materials involves complex mechanisms of converting mechanical acoustic energy into heat. In this work, the effective piezoelectric properties of polyethylene ferroelectret foams on sound absorption were investigated by comparable samples with and without the piezoelectric response. Corona poling and thermal annealing treatments were applied to the samples in order to enable and remove the piezoelectric property, respectively, while the microstructure and the mechanical properties remained substantially unchanged.

Intercalation-driven ferroelectric-to-ferroelastic conversion in a layered hybrid perovskite crystal.

Two-dimensional (2D) organic-inorganic hybrid perovskites have attracted intense interests due to their quantum well structure and tunable excitonic properties. As an alternative to the well-studied divalent metal hybrid perovskite based on Pb, Sn and Cu, the trivalent metal-based (eg. Sb with ns2 outer-shell electronic configuration) hybrid perovskite with the AMX formula (A = monovalent cations, M = trivalent metal, X = halide) offer intriguing possibilities for engineering ferroic properties.

Hybrid versus distance learning environment for a paediatric dentistry course and its influence on students' satisfaction: a cross-sectional study.

Background: During the novel COVID-19 pandemic, many universities adopted distance and hybrid learning as a modification to their teaching methods to ensure continuity of education, abiding by the worldwide recommendations of social distancing.

Aim: To compare learning environments created through hybrid learning versus distance learning, to deliver paediatric dentistry course, and to assess the correlation between the created learning environment and students' satisfaction.

Method: In this cross-sectional study, students enrolled in a hybrid paediatric dentistry course were asked to participate in an electronic survey.

Validation of the Arabic translation of the caries impacts and experiences questionnaire for children.

Background: The recently developed Caries Impacts and Experiences Questionnaire for Children (CARIES-QC) is originally an English questionnaire targeting the assessment of caries-related quality of life from a child's point of view.

Aim: This study aimed to translate and adapt the CARIES-QC into the Arabic language and to test its reliability and validity on Arabic-speaking children.

Design: A total of 234 children aged 5-16 years answered the translated questionnaire.

Enabling Distributed Intelligence with Ferroelectric Multifunctionalities.

Distributed intelligence involving a large number of smart sensors and edge computing are highly demanded under the backdrop of increasing cyber-physical interactive applications including internet of things. Here, the progresses on ferroelectric materials and their enabled devices promising energy autonomous sensors and smart systems are reviewed, starting with an analysis on the basic characteristics of ferroelectrics, including high dielectric permittivity, switchable spontaneous polarization, piezoelectric, pyroelectric, and bulk photovoltaic effects. As sensors, ferroelectrics can directly convert the stimuli to signals without requiring external power supply in principle.

Electromechanically Active As-Electrospun Polystyrene Fiber Mat: Significantly High Quasistatic/Dynamic Electromechanical Response and Theoretical Modeling.

Flexible and lightweight pressure sensors have attracted tremendous attention as a promising component of wearable biological motion sensors and artificial electronic skins. Here, the electromechanical response of as-electrospun fiber mats composed of a commodity polymer, atactic polystyrene, which can be applied in low-cost/large-area, flexible, and lightweight pressure sensors is demonstrated. The fiber mat demonstrates a significantly high apparent converse piezoelectric constant of >30 000 pm V under static measurement and ≈13 000 pm V even at a high frequency of 1 kHz.

Structure and High Performance of Lead-Free (KNa)NbO Piezoelectric Nanofibers with Surface-Induced Crystallization at Lowered Temperature.

Lead-free potassium and sodium niobate (KNN) nanofiber webs with random and aligned configurations were prepared by the electrospinning process from polymer-modified chemical solution. The crystallization process, structure, composition, dielectric, ferroelectric, and piezoelectric properties of the nanofibers and nanofiber webs were investigated. Theoretical analysis and experimental results showed that the surface-induced heterogeneous nucleation resulted in the remarkable lower crystallization temperature for the KNN nanofibers with the {100} orientation of the perovskite phase in contrast to the bulk KNN gel and thus well-controlled chemical stoichiometry.

Case Report: Clinical manifestation and dental management of Papillon-Lefèvre syndrome.

Papillon-Lefèvre syndrome (PLS) is considered a rare syndrome, which is characterized by the presence of palmar-plantar hyperkeratosis and aggressively progressing periodontitis that finally leads to premature loss of both deciduous and permanent teeth. A four-year-old Egyptian boy presented with a maternal complaint that her child suffers from early loss of many teeth, presence of loose teeth along with an asymptomatic swelling related to the upper anterior area. The patient was diagnosed with PLS.